KR100832372B1 - Ceramic powder, electroconductive paste using same, multilayer ceramic electronic component, and method for production thereof - Google Patents

Abstract

In the multilayer ceramic electronic component, it is possible to improve insulation and durability under high temperature load, and to provide a highly reliable multilayer ceramic electronic component.

In a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, a ceramic powder added to a conductive paste for forming an internal electrode layer, which has a perovskite crystal structure, the content of the tetragonal phase Wt and the content of the cubic phase Wc Ceramic powder having a weight ratio of Wt / Wc of 2 or more is used. The weight ratio Wt / Wc of the tetragonal phase and the cubic phase is obtained by polyphase analysis by the Rietveld method. The ceramic powder is, for example, barium titanate powder.

Dielectric ceramic layer, internal electrode layer, ceramic powder, perovskite crystal structure, tetragonal phase, cubic phase, weight ratio, Rietveld method, specific surface area, conductive paste

Description

CERAMIC POWDER, ELECTROCONDUCTIVE PASTE USING SAME, MULTILAYER CERAMIC ELECTRONIC COMPONENT, AND METHOD FOR PRODUCTION THEREOF

1 is a schematic sectional view showing one configuration example of a multilayer ceramic capacitor.

FIG.2 (a)-(e) is a figure which shows typically the state of the change of the X-ray diffraction chart of barium titanate powder.

Fig. 3 (a) is an X-ray diffraction chart of a tetragonal phase and a cubic phase, and (b) is an X-ray diffraction chart when assuming a mixed phase.

(Explanation of the sign)

1 multilayer ceramic capacitor

2 dielectric ceramic layers

3 internal electrode layer

4, 5 external electrode

6 Sheath dielectric layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic powder added as a common material to an internal electrode layer in a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, and in particular, to a ceramic powder useful in improving insulation of a multilayer ceramic electronic component. will be. Furthermore, the present invention relates to a conductive paste using the ceramic powder, a multilayer ceramic electronic component, and a method of manufacturing the same.

For example, a multilayer ceramic capacitor, which is one of multilayer ceramic electronic components, has a structure in which a plurality of dielectric ceramic layers and internal electrode layers are alternately stacked, and is widely used as a small, large capacity, and highly reliable electronic component. It is not uncommon for multiple multilayer ceramic capacitors to be used in one electronic device.

In recent years, miniaturization and high performance of electronic devices have been progressed, and along with this, demands for further miniaturization, large capacity, low cost, high reliability, and the like of multilayer ceramic capacitors have become increasingly strict. Therefore, in response to this, for example, in order to miniaturize and increase the capacity of a multilayer ceramic capacitor, it is necessary to make the dielectric ceramic layer thin or increase the number of laminated layers. When the dielectric ceramic layer constituting the multilayer ceramic capacitor is thinned and the number of stacked layers is increased, the above-mentioned miniaturization and large capacity can be achieved.

By the way, in consideration of the thinning of the dielectric ceramic layer and the increase in the number of laminations, it is disadvantageous to form the internal electrode layer using a conductive paste for internal electrodes mainly composed of noble metals such as Pd from the viewpoint of manufacturing cost. Do. When the internal electrode layer is formed using a conductive paste for internal electrodes mainly composed of noble metals such as Pd, the electrode formation cost increases significantly with the increase in the number of stacked layers. Therefore, a conductive paste for an internal electrode mainly composed of nonmetals such as Ni has been developed, and a multilayer ceramic capacitor and the like having an internal electrode layer formed thereon have been put into practical use.

However, when the internal electrode layer is formed of the conductive paste for internal electrodes mainly composed of nonmetals such as Ni, the thickness of the dielectric ceramic layer is 10 µm or less, or the number of laminated layers is 100 or more. The influence of the shrinkage and expansion of the internal electrode layer and the difference in the shrinkage behavior of the dielectric ceramic layer becomes remarkable, and there is a concern that a crack may occur, leading to a problem of poor manufacturing yield.

In order to solve this problem, it is effective to suppress the shrinkage of the Ni powder in the firing step, and the same powder as the ceramic powder contained in the dielectric paste in the conductive paste for the internal electrodes used to form the internal electrode layers. Adding a material as a common material is performed (for example, refer patent document 1). By adding a common material to the conductive paste, the sintering start temperature of the conductive paste is brought close to the sintering start temperature of the ceramic molded body, and the shrinkage rate at the time of sintering is brought close to the ceramic molded body to suppress the occurrence of cracks. .

[Patent Document 1] Japanese Patent Application Laid-Open No. 2005-347288

However, since the ceramic powder, which is a common material in the conductive paste, has a smaller particle size than the ceramic powder used as the base material of the dielectric ceramic layer, it is highly reactive and grows by combining the common materials, causing particle size variation of the sintered body, resulting in high insulation and high insulation. There exists a possibility of causing the problem that desired electrical characteristics are not acquired, such as deteriorating durability at the time of on-load.

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-described conventional situation, and improves insulation and durability at high temperature loads even when the thickness of the dielectric ceramic layer constituting the multilayer ceramic electronic component is increased or the number of laminated layers is increased. An object of the present invention is to provide a ceramic powder and a conductive paste that can be formed. In addition, an object of the present invention is to realize a highly reliable multilayer ceramic electronic component having excellent insulation and durability under high temperature loads by providing the ceramic powder and conductive paste, and furthermore, to provide a manufacturing method thereof. It is done.

In order to achieve the above object, the inventors have conducted various studies over a long period of time. Specifically, the ceramic powder used for the common material of the internal electrode layer of a laminated ceramic electronic component has been further analyzed. As a result, the ceramic powder having a perovskite crystal structure includes a tetragonal phase and a cubic phase, and in order to improve insulation in a multilayer ceramic electronic component and durability at high temperature loads, The knowledge that it is effective to optimize the ratio (weight ratio) of these tetragonal phase and a cubic phase was acquired.

The present invention has been completed based on these findings. That is, the ceramic powder of the present invention is a ceramic powder added to a conductive paste for forming the internal electrode layer of a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, and have a perovskite crystal structure. When the weight ratio Wt / Wc of the phase content Wt and the cubic phase content Wc is X, it is characterized by being X? 2.

The conductive paste of the present invention is a conductive paste for forming the internal electrode layer of a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, and contains a conductive material and ceramic powder, and the ceramic powder as the ceramic powder. It is characterized by containing a powder. The multilayer ceramic electronic component of the present invention is a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, wherein the internal electrode layer is formed by forming an electrode precursor layer by the conductive paste and firing the same. In the method for manufacturing a multilayer ceramic electronic component of the present invention, when the dielectric green sheet and the electrode precursor layer are alternately formed by using a dielectric paste and a conductive paste, and then fired to form a multilayer ceramic electronic component as the conductive paste, It is characterized by using the said electrically conductive paste.

Until now, little has been studied about which ceramic powder should be used for the ceramic powder used as a common material for the conductive paste. Basically, the same one as the ceramic powder for forming the dielectric ceramic layer was used. In this invention, the analysis about the ceramic powder used as said common material is repeated, and this is optimized.

For example, in barium titanate having a perovskite crystal structure, the X-ray diffraction chart also changes in accordance with the change of the specific surface area. The present inventors presume that the change of the X-ray diffraction chart is due to the mixed phase of the tetragonal phase and the cubic phase, and the multi-phase analysis (for example, the tetragonal phase with the Rietveld method) is performed on the X-ray diffraction chart. Two-phase analysis assuming two phases of cubic phase) was carried out, which was in good agreement with the above conjecture, and supported that the conjecture was correct. As a result of further analysis, it was found that the ratio of the tetragonal phase and the cubic phase was changed depending on the production conditions of barium titanate and the like, which influenced the characteristics. In other words, when the weight ratio Wt / Wc of the tetragonal phase content Wt and the cubic phase content Wc in the ceramic powder added to the internal electrode layer as the common material is X, X≥2, insulation and durability at high temperature load Is improved.

(The best form to carry out invention)

Hereinafter, the ceramic powder and the conductive paste to which the present invention is applied, as well as the multilayer ceramic electronic component (here, the multilayer ceramic capacitor) using the same, and a manufacturing method thereof will be described in detail.

First, the multilayer ceramic capacitor in which the ceramic powder of the present invention is used will be described. As shown in FIG. 1, in the multilayer ceramic capacitor 1, a plurality of dielectric ceramic layers 2 and internal electrode layers 3 alternately. It is laminated | stacked and the element main body is comprised. The internal electrode layers 3 are stacked on two opposite end faces of the device main body so that the side cross sections are alternately exposed, and a pair of external electrodes 4 and 5 are connected to these internal electrode layers 3 at both end ends of the device main body. Formed. In the device body, the exterior dielectric layer 6 is disposed at both ends of the dielectric ceramic layer 2 and the internal electrode layer 3 in the stacking direction, but the exterior dielectric layer 6 mainly serves to protect the device main body. It is formed as an inert layer.

Although the shape of an element main body is not specifically limited, Usually, it is a rectangular parallelepiped shape. There is no restriction | limiting in particular also in the dimension, What is necessary is just to set it to a suitable dimension according to a use. For example, 0.6 mm to 5.6 mm (preferably 0.6 mm to 3.2 mm) x 0.3 mm to 5.0 mm (preferably 0.3 mm to 1.6 mm) x thickness 0.1 mm to 1.9 mm (preferably 0.3 mm) ˜1.6 mm).

The dielectric ceramic layer 2 is made of a dielectric ceramic composition, and is formed by sintering a powder (ceramic powder) of the dielectric ceramic composition. The dielectric ceramic composition is composed of the composition formula ABO ₃ , wherein A site is composed of at least one element selected from Sr, Ca, and Ba. B site is composed of at least one element selected from Ti and Zr. It is preferable to contain, as a main component, a dielectric oxide having a perovskite crystal structure represented by). Here, the amount of oxygen (O) may be slightly biased from the stoichiometric composition of the composition formula. Among the above dielectric oxides, A site is mainly composed of Ba, B site is composed mainly of Ti, and barium titanate is preferable. More preferably, it is barium titanate represented by the composition Ba _m TiO _{2 + m} (wherein 0.995 ≦ m ≦ 1.010 and 0.995 ≦ Ba / Ti ≦ 1.010).

The dielectric ceramic composition may contain various subcomponents in addition to the main component. As the subcomponent, at least one selected from oxides of Sr, Zr, Y, Gd, Tb, Dy, V, Mo, Zn, Cd, Ti, Sn, W, Ba, Ca, Mn, Mg, Cr, Si and P Is illustrated. By adding the subcomponent, low-temperature firing is possible without degrading the dielectric properties of the main component. In addition, poor reliability in the case where the dielectric ceramic layer 2 is thinned can be reduced, thereby enabling a long service life.

Various conditions such as the number of layers and the thickness of the dielectric ceramic layer 2 may be appropriately determined depending on the application or the like. About the thickness of the dielectric ceramic layer 2, it is about 1 micrometer-about 50 micrometers, Preferably it is 5 micrometers or less. From the viewpoint of miniaturizing and increasing the capacity of the multilayer ceramic capacitor, the thickness of the dielectric ceramic layer 2 is preferably 3 µm or less, and the number of laminated ceramic ceramic layers 2 is preferably 150 or more.

The conductive material included in the internal electrode layer 3 is not particularly limited, but non-metals such as Ni, Cu, Ni alloy or Cu alloy can be used. What is necessary is just to determine the thickness of the internal electrode layer 3 suitably according to a use, etc., for example, about 0.5 micrometer-about 5 micrometers, Preferably it is 1.5 micrometers or less.

The conductive material included in the external electrodes 4 and 5 is not particularly limited, but Cu, Cu alloy, Ni, Ni alloy, Ag, Ag-Pd alloy, or the like is usually used. Cu, Cu alloys, Ni and Ni alloys are advantageous because they are inexpensive materials. What is necessary is just to determine the thickness of the external electrodes 4 and 5 suitably according to a use etc., for example, about 10 micrometers-50 micrometers.

In the multilayer ceramic capacitor 1 having the above-described configuration, the ceramic powder (common material) contained in the conductive paste used to form the internal electrode layer 3 greatly influences the characteristics. In this invention, insulation etc. are improved by optimizing the ceramic powder used as said common material. Specifically, powder X-ray diffraction analysis is performed on the ceramic powder having a perovskite crystal structure, and the powder X-ray diffraction results are subjected to, for example, polyphase analysis by Rietveld method, and tetragonal. When the weight ratio Wt / Wc of the phase content Wt and the cubic phase content Wc is X, a ceramic powder having X ≧ 2 is used.

Hereinafter, the polyphase analysis by the Rietveld method will be described. For example, in powder X-ray diffraction, the lattice constant from the peak position, the crystal structure parameters (polarization coordinate, occupancy ratio, atomic displacement parameter, etc.) from the area (integration intensity) of the diffraction profile, the lattice deformation and crystallite size from the enlargement of the profile The mass fraction can be grasped from the scale factor of each phase in the mixture. In powder neutron diffraction, the magnetic moment of each magnetic atom site can also be grasped from the integral intensity.

The Rietveld method is a general-purpose powder diffraction data analysis technology that can simultaneously obtain fundamental physical quantities in solid physics, chemistry, and material chemistry, and is a tool for understanding the physical phenomena and chemical properties of polycrystalline materials from structural aspects. . An important purpose of the Rietveld method is to refine the crystal structure parameters included in the crystal structure factor F _k . The structure parameters and lattice constants are directly refined for the entire powder X-ray diffraction pattern or the powder neutron diffraction pattern. In other words, the diffraction pattern calculated on the basis of the approximation structure model is fitted so as to match the measured pattern as well as possible. As a great advantage of the Rietveld method, the entire analysis pattern is subjected to fitting, and in the case of characteristic X-rays, the presence of K _α2 reflection is also taken into consideration, so that not only the crystal structure parameter but also the lattice constant is obtained with high accuracy and precision. The deformation | transformation, the crystallite size, and the thing which can quantify content of each component in a mixture are mentioned.

In the case of ceramic powder having a perovskite crystal structure, for example barium titanate, the presence of a tetragonal phase and a cubic phase is known. For example, the X-ray diffraction pattern changes in accordance with the change of the average particle diameter (specific surface area). Fig. 2 shows the state of change of the X-ray diffraction pattern in barium titanate. In the X-ray diffraction of barium titanate, when the average particle diameter is large (small surface area), two peaks of tetragonal phase are observed as shown in Fig. 2A. On the other hand, when the average particle diameter gradually decreases (the specific surface area gradually increases), as shown in Figs. 2 (b) to 2 (d), the two peaks become gradually unclear and finally, Fig. 2 ( As shown in e), it becomes a cubic phase single peak.

Here, the present inventors, for example, the state shown in Fig. 2 (b) to Fig. 2 (d) and the X-ray diffraction chart of the tetragonal phase as shown in Fig. 3 (a) and Fig. 3 (b); Assuming that the diffraction X-ray charts of cubic phases are superimposed (that is, the ceramic powder is a mixed phase of tetragonal and cubic phases), a multiphase analysis (here two-phase analysis) by the Rietveld method is attempted on the X-ray diffraction chart. did. In addition, about the multiphase analysis by the said Rietveld method, it is not only limited to the said two-phase analysis but it can also be set as three-phase or more analysis, for example.

As a result, first, the two-phase analysis result was excellent in precision and suggested that accurate analysis was performed. This can be said to support that the above assumptions (the assumption of mixed tetragonal and cubic phases) were correct, and that ceramic powders having a relatively small average particle diameter (larger specific surface area) were mixed with tetragonal and cubic phases. I figured it out. So far, barium titanate powder has not been recognized as a mixed phase of tetragonal phase and cubic phase.

Secondly, when used as a common material when forming the internal electrode layer 3 of the multilayer ceramic capacitor 1, the ratio of the tetragonal phase and the cubic phase affects the characteristics, particularly in the case of emphasis on crack suppression or the like. When the weight ratio Wt / Wc of the content Wt of the tetragonal phase and the content Wc of the cubic phase was X, it was found that X≥2 was advantageous. By setting X ≧ 2, even when the dielectric ceramic layer 2 constituting the multilayer ceramic capacitor 1 is thinned or the number of laminated layers is increased, it is possible to improve insulation and durability at high temperature loads.

Even if the said weight ratio X changes with manufacturing conditions of a ceramic powder, etc., for example, and looks like the same X-ray diffraction chart, when the multiphase analysis by the said Rietveld method is actually performed, the said weight ratio X may become a different value. have. Such a difference cannot be grasped by the conventional X-ray diffraction analysis, and it is necessary to obtain the value by polyphase analysis by the Rietveld method and select one that satisfies the above condition.

As for the weight ratio Wt / Wc (= X) of the content Wt of the tetragonal phase and the content Wc of the cubic phase, as described above, X≥2 serves as a criterion for selection of the ceramic powder having a perovskite crystal structure. In this case, it is a premise that it is a mixed phase of a tetragonal phase and a cubic phase, Therefore, the case of the tetragonal phase alone (the value of X is zero) is not included. In addition, about the value of said X, even if it devises manufacture conditions etc., there is a limit naturally, and it is about 5 (hence X <= 5) even if it is maximum. More preferably, X≤3.00. To produce a ceramic powder such as X> 3 and a specific surface area SSA of 10 m ² / g, a heat treatment and a grinding step for increasing the tetragonal phase are required, which is undesirable in terms of production cost.

In the present invention, it is an object to improve the insulation characteristics and the like while thinning the dielectric ceramic layer 2, and therefore, the thickness of each dielectric ceramic layer 2 is preferably 3 mu m or less as described above, and the internal electrode layer is It is preferable that the thickness of (3) shall be 1.5 micrometers or less. Corresponding to this, the ceramic powder used as a common material in the formation of the internal electrode layer 3 is preferably at least 10 m ² / g of specific surface area. When the specific surface area SSA is 10 m ² / g, the average particle diameter is approximately 0.1 mu m. When the specific surface area SSA of the ceramic powder used as a common material is small (average particle size is large), the internal electrode layer 3 becomes difficult to be thinned.

As described above, in the multilayer ceramic capacitor 1, the raw material (ceramic powder) selected by the raw material selection method based on the polyphase analysis by the Rietveld method is used as a common material when forming the internal electrode layer 3. Further miniaturization and large capacity of the ceramic capacitor 1 can be realized. Then, the manufacturing method of the multilayer ceramic capacitor using the said ceramic powder is demonstrated.

In order to manufacture the multilayer ceramic capacitor having the above-mentioned structure, a dielectric green sheet which becomes the dielectric ceramic layer 2 after firing, an electrode precursor layer which becomes the internal electrode layer 3 after firing, and also an outer dielectric layer 6 An exterior green sheet is prepared, these are laminated | stacked, and a laminated body is formed.

The dielectric green sheet can be formed by preparing a dielectric paste containing ceramic powder, applying it onto a carrier sheet as a support by a doctor blade method or the like and drying it. The dielectric paste is prepared by kneading a ceramic powder as a base material and an organic vehicle or an aqueous vehicle. What is necessary is just to select the average particle diameter and specific surface area according to the thickness of the dielectric ceramic layer 2, when preparing this dielectric paste.

In addition, the organic vehicle used for preparation of the said dielectric paste dissolves the binder in the organic solvent. The binder used for an organic vehicle is not specifically limited, What is necessary is just to select suitably from various general binders, such as ethyl cellulose and polyvinyl butyral. Moreover, the organic solvent used for an organic vehicle is not specifically limited, What is necessary is just to select suitably from various organic solvents, such as terpineol, butyl carbitol, acetone, and toluene. The aqueous vehicle is obtained by dissolving a water-soluble binder or a dispersant in water, and is not particularly limited as a water-soluble binder. For example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, or the like may be used.

In addition, an electrode precursor layer is formed by printing a conductive paste containing a conductive material in a predetermined region of the dielectric green sheet. A conductive paste is prepared by kneading a conductive material, a common material (ceramic powder), and an organic vehicle. As said common material, the ceramic powder which satisfy | fills the requirements mentioned before (that is, the weight ratio Wt / Wc of the content Wt of a tetragonal phase and content Wc of a cubic phase is 2 or more) is used.

After the laminate is formed, debinder treatment, firing, and heat treatment for reoxidizing the dielectric ceramic layer 2 and the outer dielectric layer 6 are performed to obtain a sintered body (element body). The heat treatment for debinding treatment, firing and reoxidation may be performed continuously or may be performed independently of each other.

The binder removal processing may be performed under ordinary conditions. However, when nonmetals such as Ni and Ni alloy are used as the conductive material of the internal electrode layer 3, it is preferable to perform the binder under the following conditions. That is, the temperature increase rate is 5 to 300 ° C / hour, in particular 10 to 50 ° C / hour, the holding temperature is 200 to 400 ° C, particularly 250 to 340 ° C, and the holding time is 0.5 to 20 hours, especially 1 to 10 time, and a mixed gas of N ₂ and H ₂ in a wet atmosphere.

As the firing conditions, the temperature increase rate is 50 to 500 ° C / hour, in particular 200 to 300 ° C / hour, the holding temperature is 1100 to 1300 ° C, especially 1150 to 1250 ° C, and the holding time is 0.5 to 8 hours, especially 1 to 3 hours, and preferably in a mixed gas of N ₂ and h ₂ in a wet atmosphere.

At the time of firing, the oxygen partial pressure in the atmosphere is preferably 10 ⁻² Pa or less. If the oxygen partial pressure exceeds the above range, the internal electrode layer 3 may be oxidized. However, if the oxygen partial pressure is too low, the electrode material will abnormally sinter and the internal electrode layer 3 tends to break in the middle. Therefore, the oxygen partial pressure of the minor component atmosphere is preferably set to 10 ^-2 Pa to 10 ^-8 Pa.

The heat treatment after firing is usually performed at a holding temperature or a maximum temperature of at least 1000 ° C, preferably at 1000 ° C to 1100 ° C. If the holding temperature or the maximum temperature is less than 1000 ° C, the oxidation resistance of the dielectric material is insufficient, so the insulating resistance life tends to be shortened. If the holding temperature or the maximum temperature is higher than 1100 ° C, the conductive material Ni in the internal electrode layer 3 is oxidized. This may adversely affect the capacity and lifetime of the multilayer ceramic capacitor.

The atmosphere of the heat treatment is an oxygen partial pressure higher than that of calcination, preferably 10 ^-3 Pa to 1 Pa, more preferably 10 ^{-2 to 1} Pa. If the oxygen partial pressure of the heat treatment atmosphere is less than the above range, it is difficult to reoxidize the dielectric layer. On the contrary, if the above oxygen range is exceeded, the internal electrode layer 3 may be oxidized. The conditions of the heat treatment are 0 to 6 hours, especially 2 to 5 hours, the cooling rate to 50 to 500 ° C / hour, especially 100 to 300 ° C / hour, and a humidified N ₂ gas or the like. It is done.

Finally, the external electrodes 4 and 5 are formed in the element body, which is the obtained sintered body, to obtain the multilayer ceramic capacitor 1 shown in FIG. The external electrodes 4 and 5 may be formed by, for example, polishing the cross section of the sintered body by barrel polishing, sand blasting, or the like, and then heating and applying the external electrode paint.

(Example)

Hereinafter, specific examples to which the present invention is applied will be described based on experimental results.

XRD (powder X-ray diffraction) measurement

Powder X-ray diffraction (XRD) measurement was performed using a powder X-ray diffraction apparatus (trade name Rint2000, manufactured by Rigaku Corporation) to obtain XRD profile data for Rietveld analysis. At this time, the measurement was performed by setting the current and the voltage so that the step width was 0.01 ° and the maximum peak count was about 10000 counts.

Rietveld Analysis

The obtained XRD profile was analyzed using Rietbelt analysis software RIETAN-2000 (Rev. 2.4.1) (for Windows). In obtaining the mass fraction of each phase, the microabsorption was correct | amended and the mass fraction was calculated | required.

Review on the reliability of polyphase analysis by Rietveld method

The analysis by the Rietveld method was attempted for the barium titanate powder having a perovskite crystal structure (specific surface area SSA 6.16 m ² / g, average particle diameter of 0.16 μm by scanning electron microscope SEM). There are three types of Rietveld analysis: an analysis as a tetragonal phase (quadric crystal) single phase, an analysis as a cubic phase (cubic crystal) single phase, and an analysis as two phases of the tetragonal phase (square crystal) + cubic phase (cubic crystal). Table 1 shows the reliability factors in each analysis.

Among the indicators for evaluating the Rietveld analysis and the degree of agreement between the observed and calculated strengths, the most important R factor is Rwp. However, since Rwp is influenced by diffraction intensity or background intensity, the index S value (= Rwp / Re) for comparing Re and Rwp equal to the statistically expected minimum Rwp is helpful as a practical measure of the accuracy of the analysis. Becomes S = 1 means perfection, and if S is less than 1.3, satisfactory analysis results will not be affected. From this point of view, Table 1 shows that the s value of the result analyzed as two phases of tetragonal and cubic crystals is 1.3 or less, and the s value is smaller than that of the single phase analysis, and the analyzed ceramic powder has two phases of tetragonal and cubic crystals. It is reasonable to think that it is.

Examination about the weight ratio Wt / Wc (= X) of the content Wt of the tetragonal phase in the ceramic powder and the content Wc of the cubic phase

Using various ceramic powders (barium titanate powder), a multilayer ceramic capacitor was produced in accordance with the above-described manufacturing method (Examples 1 to 4 and Comparative Examples 1 to 3). The produced multilayer ceramic capacitor had a size of 1.0 mm x 0.5 mm x 0.5 mm, the number of laminated dielectric ceramic layers was 160, the thickness per dielectric ceramic layer was 1.6 µm, and the thickness of the internal electrode layers was 1.0 µm. Specific surface area SSA of the ceramic powder (common material) included in the conductive paste used to form the internal electrode layer, average particle diameter (SEM particle diameter) measured by a scanning electron microscope, content of tetragonal phase Wt, content Wc of cubic phase, and the weight thereof Table 2 shows the ratio Wt / Wc (= X), the particle size of the sintered compact, the variation (standard deviation) σ of the sintered compact, the IR failure rate and the IR lifetime of the manufactured multilayer ceramic capacitor.

In Table 2, when it is determined that the particle size deviation sigma <0.10, IR defect rate <50/1000, IR life> 100 of the sintered body is good, the weight ratio Wt / Wc (tetragonal phase and cubic phase) in the ceramic powder used as the common material By setting = X) ≥2, all items are determined to be good. On the other hand, if the weight ratio Wt / Wc is less than 2, neither characteristic is sufficient.

In this invention, the weight ratio Wt / Wc (= X) of the tetragonal phase content Wt and the cubic phase content Wc is employ | adopted as an index of selection of a raw material (ceramic powder). By using the ceramic powder selected on the basis of these indices as a common material for the internal electrode layers, even if the dielectric ceramic layer constituting the multilayer ceramic electronic component is increased or the number of laminated layers is increased in accordance with miniaturization or large capacity, for example, insulation and high temperature are required. It is possible to improve durability at the time of load and to improve reliability.

Claims (10)

A ceramic powder added to a conductive paste for forming the internal electrode layer of a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, The ceramic powder which has a perovskite type crystal structure and is X <= 2 when the weight ratio Wt / Wc of content Wt of a tetragonal phase and content Wc of a cubic phase is X. The ceramic powder according to claim 1, wherein the content Wt of the tetragonal phase and the content Wc of the cubic phase are values obtained by polyphase analysis by the Rietveld method. The ceramic powder according to claim 1 or 2, wherein the specific surface area is 10 m ² / g or more. The ceramic powder according to claim 1 or 2, wherein the ceramic powder contains barium titanate powder as a main component. A conductive paste for forming an internal electrode layer of a multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked, A conductive paste containing a conductive material and a ceramic powder, and comprising the ceramic powder according to claim 1 or 2 as the ceramic powder. 6. The conductive paste according to claim 5, wherein the conductive material contains a base metal as a main component. 7. The electrically conductive paste of claim 6, wherein the nonmetal is Ni. A multilayer ceramic electronic component in which a dielectric ceramic layer and an internal electrode layer are alternately stacked. The said internal electrode layer is formed by forming an electrode precursor layer by the electrically conductive paste of Claim 5, and baking this, The laminated ceramic electronic component characterized by the above-mentioned. The multilayer ceramic electronic component of claim 8, wherein the multilayer ceramic capacitor is a multilayer ceramic capacitor. When the dielectric green sheet and the electrode precursor layer are alternately laminated by a dielectric paste and a conductive paste, and then fired to form a multilayer ceramic electronic component, A method for producing a multilayer ceramic electronic component, wherein the conductive paste according to claim 5 is used as the conductive paste.

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